The present invention is concerned with the fabrication of a semiconductor device of indium antimonide. The present invention is particularly concerned with the fabrication of MOSFET semiconductor devices and bipolar transistor devices from indium antimonide.
It has been known that indium antimonide is the highest mobility of the known semiconducting materials. Accordingly, indium antimonide has been considered as an interesting material for the fabrication of semiconductor devices.
One very important commercial type of semiconductor device is the MOSFET. Accordingly, the preparation of a MOSFET from indium antimonide would be desirable. However, MOSFETs have not been prepared from indium antimonide.
The failure to provide MOSFET devices from indium antimonide is believed to be due to the inability of the prior art to suggest a process which enables the preparation of a device having a combination of all of the necessary properties without adversely affecting any of the critical characteristics of the device.
For instance, it is essential in the preparation of a MOSFET, that an active doping impurity be introduced into only preselected local regions of the indium antimonide substrate while preventing its introduction into the substrate at undesired regions. In addition, is it essential that the technique of incorporating the impurity does not adversely affect the oxide layer, the substrate and especially the critical oxide layersubstrate interface. Furthermore, for the types of devices with which the present invention is concerned, it is important that the bond between the substrate and oxide be as intimate as possible.
Although there have been attempts to prepare certain bipolar devices from indium antimonide, these did not involve bipolar structures wherein all of the electrical contacts were located on the same surface of the substrate and which required an insulating layer. Accordingly, such prior structures could not be fabricated to provide LSI (large scale integration) devices. In addition, these prior attempts involved nonselective thermal diffusion of an impurity and are cumbersome to carry out.
It is therefore an object of the present invention to provide a method for fabricating indium antimonide semiconductor devices which provides for the important combination of introducing an active doping impurity into preselected defined regions of the substrate while preventing its introduction into undesired regions and without adversely affecting the oxide, substrate or oxide-substrate interface of the device, while also achieving an intimate bond between the substrate and oxide.
Another object of the present invention is to enable the preparation of such semiconductor devices in a manner which is both easy and efficient to carry out. Another object of the present invention is to provide a method for preparing such semiconductor materials which enables the preparation of semiconductor devices which have a high transconductance.